Detecting needle entry into a port of an infusion device

ABSTRACT

Systems for detecting needle insertion into a port chamber of an implantable medical device include a pressure sensor. The system detects characteristic pressure profiles associated with needle insertion into the port chamber through a septum and may generate a sensory cue to a clinician that proper needle placement has been achieved. Methods for detecting needle insertion into a port chamber of an implantable medical device includes detecting characteristic pressure profiles associated with needle insertion into the port chamber through a septum.

RELATED APPLICATION

This application is a division of Ser. No. 11/693,341 filed Mar. 29,2007 entitled “Detecting Needle Entry Into a Port of an InfusionDevice”. The entire disclosure of application Ser. No. 11/693,341 isincorporated herein by reference.

FIELD

This disclosure relates, inter alia, to implantable medical devices fordelivering fluid to or withdrawing fluid from a target site within apatient. More particularly, it relates to systems, devices and methodsfor sensing insertion of a needle into a port assembly provided with animplantable medical device.

BACKGROUND

A variety of implantable infusion devices are available for treatingpatients. For example, implantable infusion devices are used fordelivering therapeutic substances to a target location of a patient. Theimplantable infusion devices are typically implanted subcutaneously in aconvenient location in the patient. An infusion catheter is typicallyconnected to an outlet of the device and positioned in the patient toallow delivery to the target location. A therapeutic substance is thentypically introduced percutaneously into the implanted device byinserting a needle into a port assembly of the device and delivering afluid containing the therapeutic substance to the device via the needle.

Because the device is implanted within the patient and cannot be seendirectly, care must be taken to ensure that the needle is properlyplaced into the port assembly before transferring liquids. If the needleis not located within the fill port assembly, delivery of the infusionmedia through the needle can result failure to adequately treat thepatient and potentially dire consequences.

Accordingly, efforts have been made to identify to the clinician alocation of the fill port assembly relative to the patient's skin priorto insertion of the needle. For example, templates are well known, andcan provide a general indication or map of the port assembly locationfollowing palpating the device's periphery through the patient's skin.Additionally, electronic and/or magnetic systems have been suggestedthat provide the clinician with additional information generallyindicative of the port assembly position. Regardless of how theclinician arrives at an initial estimation of port assembly location,upon inserting the needle through the patient's skin, the cliniciannormally must make a manual/tactile determination as to whether theneedle tip has been correctly directed to the appropriate port assemblyand has subsequently pierced through a septum covering the portassembly. Most clinician's are relatively comfortable in making thisdetermination as, based on experience, the clinician can tactilely senseor feel when the needle has been inserted through the septum. However,it is sometimes difficult to know with certainty whether the septum hasbeen accessed, especially with thick-skinned patients. Further, asimplantable therapeutic substance devices become increasingly reduced insize, the attendant tactile feedback will diminish.

In light of the above, a need exists for a sensor capable of detectingneedle presence in a port assembly of an implantable therapeuticsubstance delivery device. In addition, an indicator device forproviding the clinician with a confirmation of desired needlepositioning relative to the fill port may be desirable.

SUMMARY

The present disclosure describes, inter alia, systems, devices andmethods that can be used to detect needle entry into a port of animplantable infusion device. The methods, systems and devices may beused to detect needle entry by sensing information relating to pressurein a port chamber.

In an embodiment, a method for detecting insertion into a port chamberof an implantable infusion device is described. The device includes aport assembly defining the port chamber. The port assembly includes aseptum disposed across an opening of the port chamber to fluidly sealthe port chamber relative to an exterior of the device. The methodincludes sensing a pressure change in the port chamber and determiningwhether the sensed pressure change is indicative of insertion of theneedle through the septum into the port chamber.

In an embodiment, an implantable infusion device is described. Thedevice includes a housing and a port assembly defining a port chamber.The port assembly includes a septum disposed across an opening of thechamber to fluidly seal the port chamber relative to an exterior of thehousing. The port assembly is disposed in the housing such that thechamber is accessible by a needle through the opening and the septumfrom the exterior of the housing. The device further includes a pressuresensor in fluid communication with the port chamber, and includeselectronics disposed in the housing and operably coupled to the pressuresensor. The electronics include a computer readable medium containinginstructions that when implemented cause the device to detect, via thepressure sensor, a transient pressure increase in the port chamberassociated with insertion of a needle into the port chamber.

In an embodiment, a method is described. The method includes inserting aneedle through a septum and into a port chamber defined by a portassembly of an infusion device. The septum is disposed across an openingof the port chamber to fluidly seal the port chamber relative to anexterior of the device. The method further includes (i) sensing apressure change in a port chamber; (ii) determining whether the sensedpressure change is indicative of insertion of the needle through theseptum into the port chamber; and (iii) providing a sensory cue if thesensed pressure change is indicative of insertion of the needle throughthe septum into the port chamber.

By providing devices, systems and methods that allow for detection ofneedle entry into a port assembly of an implantable infusion deviceprior to fluid being injected, feedback may be provided to preventaccidental subcutaneous delivery, as opposed to delivery into thedevice, of therapeutic substance. In instances where the implantableinfusion device includes a large reservoir and needle entry into theport assembly is for the purposes of refilling the reservoir, accidentalsubcutaneous delivery of large quantities of therapeutic substances mayresult in dire consequences. In cases where the implantable infusiondevices contain access ports intended to deliver boluses of therapeuticsubstances to a target location in a patient, accidental subcutaneousadministration of the therapeutic substance will likely fail to resultin adequate treatment of the patient. In either case, the ability todetect needle entry into the port assembly prior to infusion of anytherapeutic substance through the needle should reduce the likelihood ofaccidental subcutaneous delivery. Further, use of a pressure sensor todetect needle entry may prove to be advantageous. For example, thepressure sensor may also be used to monitor and confirm proper fluiddelivery via the needle into the device to verify that little or nosubcutaneous leakage is occurring as a result of fluid delivery. Theseand other advantages will be readily understood from the followingdetailed descriptions when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of a perspective view of animplantable infusion system implanted in a patient.

FIGS. 2-8 are block diagrams depicting implantable infusion systems orcomponents thereof in accordance with principles of the teachingsherein.

FIG. 9 is a cross-sectional view of a portion of an implantable infusiondevice useful with the systems of FIGS. 2-8.

FIG. 10 is a graph of pressure monitored in a chamber of a port assemblyof an implantable infusion device over time, showing pressure responseto needle insertion into the chamber, and needle withdrawal from thechamber.

FIG. 11 is a graph of pressure monitored in a chamber of a port assemblyof an implantable infusion device over time, showing pressure responseto needle insertion into the chamber, needle withdrawal from thechamber, and fluid delivery into the chamber.

FIGS. 12-15 are flow diagrams of representative methods in accordancewith the principles of the teachings herein.

The drawings are not necessarily to scale. Like numbers used in thefigures refer to like components, steps and the like. However, it willbe understood that the use of a number to refer to a component in agiven figure is not intended to limit the component in another figurelabeled with the same number.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustration several specific embodiments of devices, systems andmethods. It is to be understood that other embodiments are contemplatedand may be made without departing from the scope or spirit of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense.

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified. The definitions providedherein are to facilitate understanding of certain terms used frequentlyherein and are not meant to limit the scope of the present disclosure.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

As used herein, “sensory cue” means a cue capable of being received by aperson, such as an audible, tactile, or visual cue. A visual cue mayinclude, for example, text or an image.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

The present disclosure describes, inter alia, systems, devices andmethods that can be used to detect needle entry into a port of animplantable infusion device. The methods, systems and devices may beused to detect needle entry by sensing information relating to pressurein a port chamber defined by a port assembly. As discussed herein, ithas been discovered that a transient increase in pressure can bedetected upon needle entry into a chamber of a port assembly of animplantable infusion device upon piercing of a septum disposed across anopening into the chamber, allowing for detection of needle entry intothe chamber prior to dispensing fluid from the needle.

Referring to FIG. 1, an implantable infusion device 12 having two portassemblies 40, 40′ is shown implanted in a patient. Of course, infusiondevice 12 may include one, two, three, or any number of port assemblies.As shown in FIG. 1, a catheter 34 is connected to infusion device 12.Distal portion 99 of catheter 12, which may have one or more openingsthrough which fluid may flow, is positioned at or near a target locationof patient to deliver fluid from infusion device 12 to target location.The target area depicted in FIG. 1 is the patient's spinal canal.However, it will be understood that any region of a patient's body mayserve as a target area depending on the conditions, disease, or disorderto be treated. Port assemblies 40, 40′ can be accessed percutaneously bya needle (not shown in FIG. 1), through which fluid may be delivered toinfusion device 12.

Infusion device 12 may be any device capable of delivering fluid to apatient. For example, infusion device 12 may be an access port, e.g. avascular access port, through which bolus injections from needle (notshown) are nearly immediately delivered through a catheter to a patient,or may be a device having a reservoir (not shown in FIG. 1) for holdingsolutions containing therapeutic substance to be delivered over a periodof time, such as devices containing fixed or variable rate pumps,programmable pumps, or the like. Infusion devices having a reservoirwill generally include a port assembly to allow for refilling of thereservoir.

The infusion device 12 shown in FIG. 1 has two port assemblies 40, 40′one of which may be a catheter access port and one of which may be arefill port. One exemplary device having a catheter access port and arefill port is Medtronic's SynchroMed® II implantable infusion device.Of course, virtually any other currently known or future developedimplantable infusion device can also be used in connection withprinciples described herein.

While the discussion presented herein is primarily directed to infusiondevices for delivering therapeutic substances to a patient, it will berecognized that the principles described herein may be advantageouslyapplied to devices having port assemblies for the withdrawal of fluidfrom a patient.

Referring to FIGS. 2-8B, various embodiments of systems and componentsthereof are shown in block form. FIG. 2 refers to a representativesystem 10 that includes an implantable infusion device 12, a pressuresensor 14, and an indicator device 16. Also depicted in FIG. 2 is asyringe assembly 18 including a needle 20 useful for percutaneouslyinterfacing with the implantable infusion device 12. In general terms,delivery device 12 shown in FIG. 2 includes a housing 30 that maintainsa reservoir 32. Reservoir 32 contains therapeutic substance (not shown)to be delivered to the patient, for example, via a catheter 34. Thetherapeutic substance can be any infusion agent, product, or substanceintended to have a therapeutic effect such as pharmaceuticalcompositions, genetic materials, biologics, and others (e.g., insulin,saline solution, fluoroscopy agents, etc.). Regardless, a pump and/ormetering device (or “flow regulator”) (not shown) can be provided fordictating a flow of the therapeutic substance from reservoir 32 in adesired fashion. The pump/metering device can assume a variety of forms,and device 12 can further include a propellant chamber (not shown)associated with reservoir 32 for exerting a constant, positive pressureonto the contained therapeutic substance to ensure delivery to theoutlet catheter 34. In other embodiments, the pump/metering device canbe eliminated. Regardless, infusion device 12 includes a fill portassembly 40 fluidly connected to, and otherwise defining an inlet of,reservoir 32. In more general terms, however, fill port assembly 40 canassume a conventional configuration whereby a septum 42 seals a portchamber 44 relative to an exterior of the housing 30. Port chamber 44,in turn, is in fluid communication with reservoir 32 (e.g., permanentfluid connection is established, a valve means is provided that actuatesto selectively fluidly connect port chamber 44 and reservoir 32, etc.).With this configuration, then, needle 20 can percutaneously deliver aliquid to reservoir 32 upon insertion into fill port assembly 40, and inparticular through septum 42 and into port chamber 44, such as part of areservoir refilling operation.

Referring to FIG. 3, an infusion device 12 without a reservoir is shown.In the embodiment shown in FIG. 3, as with the embodiment depicted inFIG. 2, port chamber 44, defined by port assembly 40, is accessible byneedle 20 through septum 42. Port chamber 44 is in fluid communicationwith catheter 34 such that therapeutic infused through needle 20 intoport chamber 44 will be delivered to a target area of a patient throughcatheter 34.

Regardless of the embodiment depicted, infusion device 12 may includeadditional components as known conventionally or developed in thefuture. For example, infusion device 12 can include a controller orelectronics 46, for example in the form of a digital microprocessor,although any equivalent device may be substituted for a digitalmicroprocessor; in many instances, it may also be desirable that thecontroller 46 includes data storage capabilities. Where provided, thecontroller 46 (as well as other components) can be powered by a powersupply 48 (that may be preferably be the form of a battery or otherself-contained power source). Other components can further be providedwith infusion device 12 that are not otherwise illustrated, such assafety valves, flow restrictors, etc., that may enhance operation of theinfusion device 12.

With the above general construction of the infusion device 12 in mind, apressure sensor 14 is maintained by housing 30, and is associated withport assembly 40, reservoir 32 (see, e.g., FIG. 4), or any location atwhich a pressure change in port chamber 44 can be detected by pressuresensor 14; e.g. in fluid communication with port chamber 44. In variousembodiments, and as described in greater detail below, pressure sensor14 is positioned adjacent or within the port chamber 44 of the portassembly 40. In various embodiments, pressure sensor 14 signals sensedpressure-related information to a detector circuit 50 that in turn mayprompt operation of an indicator device 16. As depicted in theembodiments shown in FIGS. 2-4, detector circuit 50 and indicator device16 are maintained by housing 30. Detector circuit 50 may be adapted orprogrammed to prompt operation of indicator device 16 based uponpressure-related information generated and signaled by pressure sensor14. For example, detector circuit 50 can be configured or programmed toprompt operation of indicator device 16 upon determining (e.g., a logiccircuit, a comparator, etc.) that the pressure sensed by the pressuresensor 14 (or as otherwise indicated by information signaled from thepressure sensor 14) is indicative of a needle 20 being inserted throughseptum 42 and into port chamber 44. In the embodiments shown in FIGS.2-4, detector circuit 50 is shown as being a component apart fromcontroller 46. In other embodiments, however, detector circuit 50 can beprovided with the controller 46 such that the controller 46 isprogrammed to operate indicator device 16 in a desired fashion. In yetother alternative embodiments, detector circuit 50 can be eliminated.

Regardless of whether indicator device 16 is acted upon by a circuit orcontroller apart from pressure sensor 14, with the embodiments depictedin FIGS. 2-4, indicator device 16 is capable of producing a sensory cueto indicate that needle 20 has entered chamber 44. For example,indicator device may produce an audible noise (e.g., constant orpulsating tones, buzzer-like noise, etc.) at a frequency and decibellevel sufficient to be audibly perceived by a clinician otherwiseinterfacing with delivery device 12 through the patient's skin.

While indicator device 16 has been described as being maintained by thehousing 30, in alternative embodiments, indicator device 16 can beprovided apart from the housing 30 or a second indicator device (notshown) can be provided external delivery device 12. For example, FIG. 5is a block diagram representing a representative system 10 that issimilar in many respects to the system 10 depicted in FIG. 2. Forexample, system 10 as depicted in FIG. 5 includes an implantableinfusion device 12 otherwise having a reservoir 32 fluidly connected toa port assembly 40. Further, system 10 as depicted in FIG. 5 includes apressure sensor 14 that is otherwise associated with the port assembly40 as previously described. In addition, system 10 depicted in FIG. 5includes an indicator device 60. However, with the embodiment depictedin FIG. 5, indicator device 60 is located apart from housing 30, forexample as part of an external programmer 62. External programmer 62 isadapted to communicate with infusion device 12 through the patient'sskin such that in various embodiments, external programmer 62 andinfusion device 12 are in wireless communication, for example, viatelemetry circuitry 64 maintained by the housing 30 and correspondingtelemetry circuitry 66 maintained by the external programmer 62 (or acomponent (e.g., a hand-held instrument) electronically coupled toexternal programmer 62). Alternatively, other forms of wirelesscommunicative links between infusion device 12 and external programmer62 can be provided.

Regardless, in various embodiments, pressure sensor 14 is electronicallycoupled to telemetry circuitry 64 (for example, via a controller (notshown)), with pressure-related information generated by pressure sensor14 being signaled to external programmer 62 via telemetry circuitries64, 66. External programmer 62 includes detector circuit 50 previouslydescribed (that can be provided as part of a controller associated withthe external programmer 62) that dictates operation of indicator device60. The parameters under which detector circuit 50 will prompt operationof the indicator device 60 are described in greater detail below. In oneembodiment, indicator device 60 is a display screen adapted to displayinformation to the clinician. As is known in the art, a display screenis commonly provided with external programmer 62 (e.g., an N′Vision™Programmer available from Medtronic, Inc., of Minneapolis, Minn. as partof the SynchroMed® II Infusion System), and can display information in avariety of fashions, for example, with text, pictures, symbols,graphical information, etc. Indicator device 60 can further include asensory cue generator, such as sound generator, as previously described.Regardless, in one embodiment, upon determining that pressure-relatedinformation generated by pressure sensor 14 is indicative of needle 20entering port chamber 44, detector circuit 50 prompts indicator device60 to inform the clinician via the display screen, sound generatingdevice, or the like. In other embodiments, detector circuit 50 can beeliminated with indicator device 60 simply displaying a current pressurereading provided by the pressure sensor 14. Under these conditions, theclinician can make a self-evaluation as to whether the sensed anddisplayed pressure is indicative of desired needle placement.

With the above description in mind, FIGS. 6-8 show alternativeembodiments of systems 10 in block form. While FIGS. 6-8 do not showsome of the features of the devices described in FIGS. 2-5, it will beunderstood that one or more of the features discussed above may beincluded. System 10 as shown in FIGS. 6-8 includes two port assemblies40, 40′. Port assembly 40 is a refill port assembly in fluidcommunication with reservoir 32, and port assembly 40′ is a catheteraccess port assembly in fluid communication with catheter 34. Pressuresensor 14, 14′ may be in fluid communication with fill port chamber 44(FIG. 6), catheter access port chamber 44′ (FIG. 7), or both (FIG. 8).As discussed above, pressure sensor 14 may be positioned anywhere thatpressure changes in a chamber 44, 44′ can be detected by sensor 14, 14′.

FIG. 9 is a simplified, cross-sectional view of an embodiment of aportion of system 10, such as the pressure sensor 14 in conjunction withrelevant portions of the infusion device 12, such as housing 30,reservoir 32, and the port assembly 40. In general terms, port assembly40 is formed in an opening 70 of housing 30 such that port assembly 40is exteriorly accessible relative to housing 30. Septum 42 is disposedacross port chamber 44 (referenced generally) defined by a wall of portassembly 40, such that septum 42 seals the opening 70 relative to theport chamber 44/reservoir 32. Septum 42 can be manufactured of anysuitable material or materials. Typically, septum 42 will be made ofelastomeric materials, for example, silicone rubber, that are pierceableby needle 20 (which itself does not necessarily form a part of thesystem 10) and compatible with the therapeutic substance (not shown) tobe contained with reservoir 32.

In various embodiments, port assembly 40 further includes a septum plug74 used to retain septum 42 while providing a fluid-tight seal. Septumplug 74 defines the port chamber 44 to include drain holes 78 that allowfluids delivered to port chamber 44 to pass into reservoir 32. In someembodiments, a valve feature (not shown) can be provided to furthercontrol flow of liquid from port chamber 44 to reservoir 32 as is knownin the art. As a point of reference, relative to an arrangement of portassembly 40, septum 42 defines a first or exterior side and a second orinterior side 82. Exterior side 80 is exposed relative to opening 70 ofhousing 30, whereas interior side 82 defines a portion of port chamber44. While FIG. 9 is described with regard to a fill port assembly 40, itwill be understood the components described with regard to FIG. 9 can bereadily applied or adapted to the catheter access port assembly.

With the above conventions in mind, pressure sensor 14 is, in variousembodiments, associated with port assembly 40, and in particular portchamber 44, by disposing the pressure sensor 14 along an interior of awall of septum plug 74. In other embodiments, pressure sensor 14 isdisposed within a thickness of septum plug 74 (such as by forming (e.g.,overmolding) septum plug 74 about pressure sensor 14). Even further,pressure sensor 14 can be assembled to an exterior of septum plug 74(relative to the port chamber 44).

Regardless of an exact location, pressure sensor 14 can assume a varietyof different forms. For example, pressure sensor 14 can be a capacitivemeasurement device which determines pressure by measuring the change incapacitance of a flexible membrane attached but insulated from aconductive, gas-filled cavity due to deflections caused by pressureapplied over the flexible membrane. Alternatively, pressure sensor 14can be a sensor that utilizes the piezo-electric effect or resistivechange due to metallic strain in order to measure pressure applied.Regardless, in various embodiments, pressure sensor 14 is adapted togenerate a signal indicative of a pressure of port chamber 44.Alternatively, pressure sensor 14 can be adapted to generate a signalindicative of a change in pressure of port chamber 44. In more generalterms, then, pressure sensor 14 is any device capable of sensing andsignaling information indicative of pressure characteristics associatedwith port chamber 44 or fluid port assembly 40 more generally. In thisregard, pressure sensor 14 can be electronically coupled to detectorcircuit 50 (FIGS. 1A, 1B) or indicator device 16 (FIGS. 2-4), 60 (FIG.5) in a variety of manners. For example, electrical wiring (not shown)can provide the desired electrical connection. Alternatively, a wirelesslink can be provided between pressure sensor 14 and the processingdevice in question.

Systems 10 as thus described can be used to confirm entry of needle 20through septum 42 into port chamber 44. Systems 10 may also be used toprovide a clinician with sufficient information to make thisdetermination (not shown).

In general terms and without being bound by the following theory, it isbelieved that insertion of needle 20 through septum 42 typicallyrequires application of a pressure exceeding a minimum threshold. Oncethe force threshold is met, needle 20 will quickly enter into portchamber 44 due to the dynamic friction force being less than the septumpuncture force. Needle 20 will thus rapidly enter port chamber 44independent of clinical technique because the transit time is typicallymuch less than human response reflex time. Rapid entry of the volume ofneedle 20 into chamber 44, that generally has a fixed volume, willresult in a rapid increase of pressure functionally related to thedisplacement volume of needle 20. The mechanical energy caused by theincreased pressure is stored in mechanisms of elastic compliance thatare present within the infusion device 12 or catheter 34. The storedenergy will dissipate out of chamber 44 by the mechanism of fluid flowthrough catheter 34 or reservoir 32 and will eventually return to theambient level. The events of rapid pressurization followed by thedissipation result in a characteristic pressure profile that can bedetected by an electronic circuit or a computer software algorithm toindicate the needle entry event. An inverse pressure profile eventoccurs during the removal of a needle from a septum.

Referring to FIG. 10, exemplary transient pressure profiles 90, 90′, 92,92′ associated with (i) needle insertion through septum into portchamber (90, 90′) and (ii) needle withdrawal from port chamber throughseptum (92, 92′) are shown. The pressure profiles depicted in FIG. 10,were obtained by inserting a needle into a SynchroMed® II pump'scatheter access port. The pump was specially fixtured with a MedtronicChronicle Pressure Sensor (which is a capacitive-based pressure sensorhaving a Titanium flexible membrane). A short segment of catheter tubingwas used to attach the pump's output port to a 1 inch titanium blocksensor housing chamber. Data was recorded using a National Instruments®data acquisition system.

Referring to FIG. 11, exemplary pressure profiles associated withinsertion of a needle into a refill port chamber, injection of fluidfrom the needle into the chamber, and needle withdrawal from the chamberare shown. The pressure profiles depicted were obtained by inserting aneedle into a SynchroMed® II pump's refill port. The pump was speciallyfixtured with a Medtronic Chronicle Pressure Sensor. The sensor wasfastened to a specially machined pump to a channel that allowedmeasurement of the pressure of the refill port. Data was recorded usinga National Instruments® data acquisition system.

As can be seen from FIGS. 10 and 11, following the insertion of a needlethrough a septum into a port chamber, a rapid increase in pressure isobserved. Within seconds, the pressure in the chamber returnssubstantially to the pressure observed prior to needle insertion orambient pressure. As shown in FIG. 11, the same pressure sensor that isused to measure pressure changes associated with needle insertion intothe port chamber can be used to measure pressure changes associated withfluid flow in to the port chamber or reservoir in fluid communicationwith the port chamber. It may be desirable for slight flow restrictionbetween the fill port chamber and the reservoir to be present to allowfor pressure increase associated with fluid flow into the port chamberto be more readily identified.

In light of the above, FIG. 12 provides a flow diagram illustrating amethod for monitoring needle insertion into a port chamber. The methodincludes sensing information relating to pressure in a port chamber(100) and determining whether the sensed information is indicative ofinsertion of a needle through a septum into a port chamber (110). Oneway to determine whether the sensed information is indicative ofinsertion of a needle through a septum into a port chamber is todetermine whether the sensed information reflects a transient pressureincrease in the chamber (e.g., as described with regard to FIGS. 10 and11). For example, it may be determined whether an increase in chamberpressure is followed by a return to a substantially similar pressure tothat prior to the pressure increase within a suitable amount of time tobe indicative of needle insertion into the port chamber. A suitableamount of time may be within 5 seconds, within 2 seconds, within 1second, etc. Alternatively, or in addition, it may be determined whetheran increase in pressure is followed by a logarithmic decay profilecharacteristic of a needle insertion into a port chamber. As the profileof various port assemblies in various infusion devices may varydepending on configuration, device components or materials, or the like,it may be desirable to (i) identify a characteristic transient pressurepattern associated with needle insertion into a port chamber of givendevice or class of devices and (ii) compare sensed pressure-relatedinformation to the characteristic transient pressure pattern todetermine whether the sensed information is indicative of needleinsertion into the port chamber.

With the above discussion in mind, FIG. 13 provides a flow diagramillustrating a method for monitoring needle insertion into a portchamber. The method includes inserting a needle into a patient in anattempt to access a port chamber of an infusion device (200) and sensinginformation relating to pressure in the port chamber (210). Adetermination may then be made as to whether the sensed information isindicative of insertion of the needle through a septum into the portchamber (220). If the sensed information is indicative of needleinsertion into the chamber, a cue may be generated to indicate that theneedle is in the chamber (230), alerting a clinician of successfulplacement of the needle. The clinician may then proceed with deliveringfluid into the chamber via the needle (240). If the sensed informationis not indicative of needle insertion into the chamber, a cue will notbe generated and the clinician may then again attempt to insert theneedle into the chamber (200).

FIG. 14 provides a flow diagram illustrating a method for monitoringneedle insertion into a port chamber similar to that shown in FIG. 13.In FIG. 14, the device is first alerted that a needle is about to beinserted into a port chamber (250); e.g., through the use of aprogrammer device. A clinician may then insert the needle into a patientin an attempt to access the port chamber of the infusion device (200).Information relating to pressure in the port chamber is sensed (210) anda determination is made as to whether the sensed information isindicative of insertion of the needle through a septum into the portchamber (220). If the sensed information is indicative of needleinsertion into the chamber, a cue may be generated to indicate that theneedle is in the chamber (230), alerting a clinician of successfulplacement of the needle. The clinician may then proceed with deliveringfluid into the chamber via the needle (240). However, if no informationindicative of needle entry into port chamber is sensed, a cue may begenerated to indicate that the needle is not in the port chamber (260),allowing the clinician, to then again attempt to insert the needle intothe chamber (200). Because the device is alerted that a needle is soonto be inserted into a port chamber (250), an actual cue may be generatedto alert the physician that no needle has been detected in the portchamber (260); e.g., if no indicative pressure information is sensedwith in a predetermined time from alerting the device. Systems capableof carrying out such methods may be desirable as compared to thosecarrying out a method described in FIG. 13, where the clinician relieson lack of a cue to determine that the needle has not been inserted intothe port chamber. The method described in FIG. 14, may also be desirablefrom a power-savings perspective. That is, it is possible to supplypower to pressure sensor, detector circuit, indicator device, etc. onlyafter the device is alerted that a needle is about to be inserted, asopposed to continuously supplying power to such components.

FIG. 15 provides a flow diagram illustrating a method for monitoringneedle insertion into a port chamber similar to that shown in FIG. 14.The method illustrated includes sensing information relating to pressurein the port chamber (270) and determining whether the sensed informationis indicative of fluid being delivered into the port chamber (280);e.g., a characteristic rise in pressure. If the sensed information isnot indicative of fluid being delivered into the port chamber, a cue maybe generated indicating that the needle is not in the port chamber(260), alerting the clinician to again attempt to insert the needle intoport chamber (200). In the absence of such a cue, the clinician maycontinue to deliver fluid into the chamber via the needle (290).

One of skill in the art will understand that components or stepsdescribed herein regarding a given embodiment or set of embodiments mayreadily be omitted, substituted, or added from, with, or to componentsor steps of other embodiments or sets of embodiments, as appropriate ordesirable.

1. An implantable infusion device comprising: a housing; a port assemblydefining a port chamber, the port assembly including a septum disposedacross the chamber to fluidly seal the port chamber relative to anexterior of the housing, the port assembly being disposed in the housingsuch that the chamber is accessible by a needle inserted through theopening and the septum from the exterior of the housing; a pressuresensor in fluid communication with the port chamber; and, electronicsdisposed in the housing and operably coupled to the pressure sensor, theelectronics including a computer readable medium containing instructionsthat when implemented determine whether a transient pressure increaseassociated with insertion of a needle into the port chamber, prior todispensing fluid into the port chamber, is detected via the pressuresensor.
 2. The device of claim 1, wherein the pressure sensor isoperably disposed in the port chamber.
 3. The device of claim 1, furthercomprising a reservoir in fluid communication with the port chamber. 4.The device of claim 1, wherein the pressure sensor is operably disposedin the reservoir.
 5. The device of claim 1, wherein the port assembly isa refill port assembly.
 6. The device of claim 1, wherein the portassembly is a catheter access port assembly.
 7. The device of claim 1,further comprising a telemetry circuit configured to transmit a signalto an external device, wherein the signal indicates whether a needleentry into the port chamber has been detected.
 8. The device of claim 1,further comprising an indicator circuit, wherein the indicator circuitis configured to generate a sensory cue indicative of detection ofneedle entry into the port chamber.
 9. The device of claim 1, whereinthe electronics are configured to determine whether the sensed pressurechange is indicative of insertion of the needle through the septum intothe port chamber, prior to dispensing fluid into the port chamber, bydetermining whether the sensed pressure change reflects a transientpressure increase in the chamber.
 10. The device of claim 9, whereindetermining whether the sensed pressure change is indicative ofinsertion of the needle through the septum into the port chamber furthercomprises determining whether the pressure in the chamber returns,within 5 seconds, to a level substantially similar to that prior to thetransient pressure increase.
 11. The device of claim 9, whereindetermining whether the sensed pressure change is indicative ofinsertion of the needle through the septum into the port chamber furthercomprises determining whether the pressure in the chamber returns,within 2 seconds, to a level substantially similar to that prior to thetransient pressure increase.
 12. The device of claim 9, whereindetermining whether the sensed pressure change is indicative ofinsertion of the needle through the septum into the port chamber furthercomprises determining whether the pressure in the chamber returns, in alogarithmic decay profile over time, to a level substantially similar tothat prior to the transient pressure increase.